Llanthony Secunda Priory is a ruined former Augustinian priory in Gloucester, England. It was founded in 1136 by Miles de Gloucester, 1st Earl of Hereford, as a retreat for the monks of Llanthony Priory, Vale of Ewyas, in what is now Monmouthshire, Wales, from persistent attacks by the local population.
The new priory flourished. By 1150 it had "stately buildings in a landscape of gardens and vineyards"; it became independent from its mother house and it amassed property both in Gloucester and the surrounding area and by the sixteenth century Llanthony Secunda was the sixth largest Augustinian house in England, owning 97 churches and 51 well-appointed manors.
After the Dissolution of the Monasteries the priory with its lands near Gloucester was granted by the Crown to Arthur Porter, MP for Gloucester. The Porters, and their descendants the Scudamores, used it as a mansion house until the Siege of Gloucester in 1643, when it became part of the Royalist camp. After the siege only outbuildings remained standing, used as a farmstead and stables. From 1794 canal, railway and industrial works gradually encroached on the site and it was used as a scrap-yard between 1974-1991. Today, the remains of Llanthony Secunda Priory are a Scheduled Monument with six Grade I Listed structures, owned by the Llanthony Secunda Priory Trust.